Manipulation of substitutional defects for realizing high thermoelectric performance in Mg3Sb2-based Zintl compounds

The introduction of point defect by extrinsic doping is an effective way to the optimization of carrier concentration. Here, we theoretically and experimentally find that Pr is a more effective dopant in Mg3Sb2 compared to Te. Using first-principles defect calculations, the predicted highest carrier concentration with Pr doping at 725 K can be up to ~9.3 × 1019 cm-3, consistent with our experimental measurement. In addition, the point defect introduced by Pr substitution on Mg sites leads to the lattice thermal conductivity to be reduced to as low as 0.429 W m-1 K-1. By optimizing the Pr doping concentration, Mg3.2Pr0.02Sb1.5Bi0.5 exhibits a peak zT value of 1.70 at 725 K.